This chapter offers a philosophical analysis of the experience of illness, viewing it as a transformative experience touching on all life domains. Using a phenomenological framework, I show how the physical and social world of the ill person changes, as well as her self-identity, and relationship to time and mortality. I deploy a set of concepts, including bodily doubt, the geography of illness, the social architecture of illness, and illness as dis-ability, to provide an account of how illness is lived, something largely absent from the medical approach. The chapter opens with Toombs’ account of illness as a series of losses. It then examines symptom experience, diagnosis, disease progression, and prognosis. Tolstoy’s The Death of Ivan Ilyich is used to exemplify the experiential dimension and existential meaning of each element. The chapter closes by suggesting that Heidegger’s definition of human existence as “being able to be” needs to be broadened to include the “inability to be” entailed by illness.